Free piston engine air pressure make-up and auxiliary supply means



Jam 13, 1948. w. A. MORAIN 2,434,230

FREE PISTON ENGINE AIR PRESSURE IAKE-UP AND AUXILIARY SUPPLY [EARS 2 Sheets-Sheet 1 Filed Oct. 9, 1944 M. mm Q mm v %m N\ w M Q $0 mm a W N a N w M Q a .u N 0 \v -m Q\ w N m 4 S. Qwm Rm & .m. m.. M m u w v Q n o 1% Q. Q l M & m i w@.\\\ Q\\ R 3 Jan. 13,1948. w, MQRAIN 2,434,280

FREE PISTON ENGINE AIR PRESSURE MAKE-UP AND AUXILIARY SUPPLY MEANS Filed Oct. 9, I944 2 Sheets-Sheet 2 Q 5 g 3 E MLLA UAMURAIN FREE PISTON ENGINE AIR PRESSURE MAKE-UP AND AUXILIARY SUPPLY MEAN S Willard A. Morain, Hamilton, Ohio, assignor, by

mesne assignments, to Lima-Hamilton Corporation, New York, N. Y., a corporation of Virginia Application October 9, 1944, Serial No. 557,798

16 Claims.

This invention relates to internal combustion engines of the free piston type and particularly to provide a self-feeding make-up air supply therefor.

In the use of an engine of this type wherein air charges are compressed in the direct and reverse bounce chambers by the action of the pistons, it is desirable for efficient engine compression to vary such charges and maintain a certain balance of pressures therein by admitting air under pressure thereto under predetermined varying running conditions and to compensate for air pressure leakage. The supplied air pressure must be at a pressure level sufficient to dominate over the pressure existing in said chambers durin a respective portion of each cycle. While this added or supplemental air supply could be taken from a separate air flask, or other source charged by an independent pressure, it is found more suitable and desirable to embody it as a selfoontained feature of the engine.

The primary object of the present invention is the provision of means in connection with an engine of the free piston type to maintain auto-' lized to supply both the direct and the reverse bounce spaces of the engine with the supplemental air pressure supply needed for efiicient running, the compression ratios of such spaces being set to give the proper energies with such a source of supplemental air supply.

Other objects and advantages of the invention will be apparent from the following detailed description, and from the accompanying drawings illustrating one embodiment thereof, and in Which Figure 1 is a diagrammatical view of a free piston engine, together with the associated direct and reverse bounce pressure governors and the connections embodying the invention; Fig. 2 is a sectional detail of the direct bounce pressure governor, and Fig. 3 is a sectional detail of the reverse bounce pressure governor.

Referring to the drawings, l designates a more or less diagrammatical showing of a free piston engine, which comprises a casing 2 formin at its center a combustion chamber 3, at each of its opposite ends an air compressor cylinder 4, and at the outer end of each of such cylinders a direct bounce chamber 5. Opposed power pistons 6, 6 operate in the combustion chamber 3 and each of these attaches to an air compressor pisinto the respective bounce chamber 5. The di-' rect bounce chambers 5 are in communication through an equalizing connection I ll, the air compressor spaces 4 are in communication through a scavenging receiver II and the reverse bounce spaces 4' have an equalizing connection l2. The scavenging receiver l I has a port connection l3 with one end portlonof the combustion chamber 3, so that its cylinder end is uncovered by the piston 6 at the end of its power or expansion stroke. An exhaust passage I4 is provided near the outer end of the combustion chamber in position to be uncovered by its closing piston 6 near the end of its power or expansion stroke, but before the opening of the scavenging port connection l3. The compressor chambers 4 have valve controlled air admission ports l5 and valve controlled exhaust ports IS, the latter opening intothe scavenging receiver H. The two onposing piston sets are connected by a suitable synchronizing means (not shown), as well understood in the art.

Nothing is claimed in the present application for the construction and operation of the engine itself, this being the invention of Frank M.

Lewis. The illustration and description thereof have, therefore, only been suflicient for the operation of the subject means, and for the operation of the direct bounce and the reverse bounce pressure governors A and B, acting in combination therewith, to be understood.

Furthermore, no novelty in this application is claimed for the direct and reverse bounce governors A and B per se, or their connection with the engine, except that the air supply for supple-v menting the air bounce chamber pressures is taken from the scavenging receiver, which constitutes one of the purposes of the present invention. Governor A is the invention of Frank M. Lewis and is claimed in application Serial No. 548,115, filed August 4, 1944, now abandoned.

The governor A, in its illustrated embodiment, includes frames or casing parts 2|, 22, the former having a projection 23 (Fig. 2) to which a pressure equalizing lever 24 is fulcrumed intermediate its ends to provide two oppositely projecting arms a and b. Fluid pressure responsive means 25, 26,

21 and 28, in the present instance,- in the form of Sylphon bellows, are interposed between the frame part 2| and lever, the first two acting outward against the lever arm a and the last two against the arm 11.

It is disclosed in the said Lewis application that in the proper operation of a free piston engine the pressure necessary to be maintained in the direct bounce space or connection of the engine is a function of the compressor pressure, the scavenging receiver pressure and the reverse bounce pressure, the necessary relationship of which can be calculated. These pressures act on the lever 24 through said means 25, 26, 21 and 28, in a manner to -hold it in equilibrium when pressures are proper, and to move it from such position when the pressures are not proper for efficient operation. The function of the governor A is to maintain automatically the proper relationship between the maximum direct bounce pressure and said other factors, namely, the a compressor weighted pressure, the scavenging receiver pressure and the maximum reverse bounce pressure.

In governor A, as-here illustrated, the bellows 25 is in connection with the compressor space 4 (Fig. 1) through the line 39, the bellows 26 is in communication with the reverse bounce space equalizer i2 through the line 3|, the bellows 21 is in communication with the direct bounce space equalizer I through the line 32, and the bellows 28 is in communication with the scavenging receiver ll throughv the connection 33.

The line-32 is through the casing part 22 ot the governor A and in this part a pressure equalizing means for said line, operating in conjunction with unbalanced movements of the lever 24, is located. In the present instance, the line 32 is through a pressure equalizing chamber 35 in the part 22, and a check valve 36 is located in the line between said chamber and the bellows 21 and opens toward the bellows. A return leak passage 31, with a needle control valve 38 therein, is provided in the connection 32 around the check valve 36 and chamber 35.

The chamber 35 has communication with a "source of air pressure supply which, in the present instance, is from the scavenging receiver line 33 through a branch 33 that is controlled by an inwardly opening check valve 39 and also by an inwardly opening check valve 40. One feature or the present invention is to have the air pressure supply for the chamber 35 from the scavenging receiver ll instead of from a source of high pressure supply, which is separate from the engine. The chamber 35 has an exhaust passage 4| with a check valve 42 therein which opens inwardly with respect to the chamber. The valves 39 and 42 are normally held seated by springs in the chamber 35 and have stems projecting therefrom away from the said chamber and into a chamber or pocket 43 in the part 22 and attached therein to the free or movable end or a fluid pressure responsive means, in the present instance, in the form of two bellows 44 and 45, respectively, which bellows connect at their opposite ends through respective ports 46 and 41 with a valve chamber 48. The communication 01' the ports 46 and 41 with the chamber 48 is controlled by a valve 49, which is spring pressed in one direction to yieldingly engage the arm b of the equalizing lever 24 in opposition to the bellows 21 and 28. The chamber 48 is in communication with an oil or other suitable hydraulic pressure supply through a line 50 and when the lever 24 is in a position of equilibrium the valve 49 stands in a position to close the communication of both ports 46 and 41 to such pressure line and when moved in one direction or the other it opens one or the other of said ports to the pressure line.

In the operation of a free piston engine, it will be understood that any variation from the predetermined normal stroke length load or speed, or upon the occurrence of any air leakage into or out of the various air chambers, will cause the relative pressure values or the bellows 25, 26, 21 and 28 to change according y, thus disturbing the equilibrium of lever 24. In regaining its equilibrium, the governor A automatically re-establishes the pressure balance of the various bellows and their respective engine chambers. A movement of' the lever to an unbalanced position is responsive to a variation of pressure in any one of the bellows, so that the right hand end 01' the lever is lowered or raised in accordance with the pressure variation. This movement or the lever either causes or permits a movement or the governor control valve 49 whereby, upon a lowering of the adjacent end of the lever, the valve plunger is moved to admit an operating pressure to the bellows 44, which in turn causes an opening of the valve 39 and an admission of air pressure from the line 33 to the direct bounce pressure line 32 to increase pressure therein an extentsuflicient to move the lever back to neutral or equilibrium, which in turn moves the valve 49 to close the bellows port 46. If the unbalancing pressure on the lever 24 is such as to raise its arm b and throw the lever out or balance, the control plunger 49 is raised, thus admitting pressure to the bellows 45 to efiect an opening of the relief valve 42, and permitting a reduction in pressure in the bellows 21 and a consequent balancing of the pressure against the lever 24 to permit it to 'retum to neutral.

, vide return leak passages from the bellows 25 and 26 around respective check valves 5|, with such passages controlled by nearly closed valves 52 and 53. It is also desirable to interpose a pressure compensating spring 54 between the frame part 2| and the arm 12 of the lever 24 and to provide an adjustment for this spring to assist in obtaining aposition of equilibrium for the lever under normal running conditions.

The reverse bounce governor'B is similar in operation to that of the direct bounce governor A, except that its control is manual instead of automatic, as in the case of'the governor A. This governor includes a frame or casing part 55 suitably mounted at a side of the associated engine I, and such casing includes a pressure equalizing chamber 56 in communication through a branch 51 with the reverse bounce equalizer line 3|, which leads in the present instance, to the bellows 26 in the direct bounce governor A. An inwardly opening check valve 58 controls the communication between the chamber 56 and, air pressure supply line 59 in the casing 55, while an inwardly opening check valve 60 controls communication between the chamber 56 and a relief passage 6i having a non-return check valve 62 therein. The air supply passage 59 connects with a branch 33 of the scavenging receiver line 33, so that the high pressure air supply to the governor B is from the scavenging receiver I l, the same as in the case of the governor A. A non-retum check valve 63 is provided either in the line 33 orthe line 59.

The two check valves 58 and 60 are normally held closed, in the present instance, by springs disposed in the chamber 56 and the stems of such valves are attached, respectively, to the free ends of Sylphon bellows 64 and 65 disposed in a recess 66 in the casing part55 and communicating at their opposite ends with a valve chamber 61 through respective passages 68 and 69. The valve endsof these passages open into annular recesses 10 and 1|, respectively, in the wall of the valve chamber 61. A high pressure oil or other suitable hydraulic pressure supply line 12 communicates with the valve chamber 61 between the two recesses 16 and II. The chamber 61 at the outer side of each recess 10, I I, with respect to the supply line 12, has communication with a leak-oil passage 13. This passage also preferably has relief communication with the chamber 61 between the two recesses and H, and a suitable control valve 14 preferably of the needle type is disposed in this communication for the purpose of bleeding air from said chamber.

A control valve of the plunger type operates in the valve chamber 61 and has two lands l6 and 11 which are spaced by a recess portion 18 in communication with the supply line 12, the positions of the lands l6 and 11 being such that a movement of the valve in one direction from normal position will uncover the recess I6 to the supply line 12, and a movement of the valve in the opposite direction will uncover the recess 1| to the supply line. It is thus apparent that when the valve is moved to the left, from normal closed position, pressure will be admitted to the bellows 64 from the supply line 12 to effect an expansion of such bellows and a consequent opening of the at the outer side of each land portion 16, H, in

communication with the relief passage 13.

A suitable fluid pressure responsive means, such for instance as a Sylphon bellows B6, is disposed in'a recess ill in the casing 55 and has a free or movable end bearing against the adjacent or left hand end of the valve 15, so that the outward or right hand movements of such valve are responsive to an expansion of the bellows. The opposite or stationary end of the bellows has communication with the reverse bounce pressure line 51, 3i, through a passage 82 in which is disposed a check valve 83 that opens inwardly toward the bellows. A slow leak passage 84 is provided in the line 82 around the check valve 83 and is controlled by a needle valve 85.

The outward movement of the valve 15 or that induced by an expansion of the bellows 80 is opposed by a coiledcompression spring 66, the outward end thrust of which is against a part 81 which is manually movable to vary the adjustment of the spring and thereby vary the englne speed. This control, in the present instance, comprises a hand lever 88 having a stationary fulcrum 89 and carrying at its handle end a trip dog 90 in engagement with a segmental ratchet part 9| to hold the lever in adjusted position. A roller 92 on the lever bears against the outer side of the thrust part 81. In practice, the reverse bounce pressure of the engine dictates to a considerable extent the engine cyclic frequency, and a raising of such pressure increases the engine speed while a lowering of the pressure reduces the speed. In this connection, it is apparent that a movement of the control lever 88 to the left will increase the pressure on thespring 86 and tend to move the valve to the left and cause a partial collapse of the bellows 80. This movement of the valve would uncover the recess 10 and permit high pressure oil from the line 12 to enter the bellows 64 and efiect an opening of the valve 58, whereby air pressur from the line 36 is permitted to enter the equalizing chamber 56 and raise the pressure in line 51. The increased pressure in such line is permitted to enter the bellows 86 and thereby neutralize the pressures acting on the valve 15. The reverse bounce pressure range is now higher and the engine speed is accordingly greater. A movement of the control lever to the right will act to permit movement of the valve 15 to the right, so that air pressure will enter the bellows and open the relief valve 66, thereby reducing the reverse bounce pressure in the line 51 and accordingly the engine speed.

For efficient operation of the engine, it is desirable to maintain the compression ratios of the direct bounce chambers as low as possible, and the present system, wherein the scavenging receiver pressure is used to supplement the direct bounce and reverse bounce pressures, effects a lowering of such ratios over what would be possible-if any of the other air spaces of'the engine were tapped. The more moderate the compression ratios in the direct bounce spaces the'more moderate is the piston velocity at the scavenging end of the stroke. pression ratios would have to be at least approximately 10 to 1 (normal full stroke), if the supply pressure were taken from any of the other spaces of the engine, the compression ratios will be reduced to approximately '7 to 1 by utilizing the scavenging receiver pressure for air supply purposes.

The use of an air supply of constant pressure such as the scavenging receiver will eliminate much of the objectionable surge phenomena which might be encountered if the supply were taken from any other space on the unit wherein the pressure is constantly varying.

In the operation of the reverse bounce governor B, it will be understood that the reverse bounce equalizer I2 is connected to this governor through the pipes 3| and 51, and that the pipe 33 from the scavenging receiver H is connected to the feed point of the governor through the line 33 and the non-return valve 63, and thence to the equalizing chamber 56 through the governor line 59 when the valve 58 is open. When the governor is in a condition demanding more air for the reverse bounce space, the valve I5 is permitted to move to the left by reason of the reduced air pressure in bellowse86, thus opening the high pressure line 12 to the bellows 64 through the passage 68 and effecting an expanding movement of the bellows 64 and a consequent opening of the valve 58 to permit air supply pressure from the scavenging receiver line to enter the equalizing chamber. This action occurs during the portion of a cycle when the scavenging air pressure predominates, and continues until the governor B is again restored to balance. When, during this action, the reverse bounce pressure predominates, loss of air back to the scavenging receiver is prevented by the non-return valve 63. As the pressure in line 82 is restored to its equilibrium value, bellows is expanded, moving valve 15 to the right, permitting it to return to its neutral position. When the governor is in a condition demanding less air for the reverse bounce space,

the valve 15 is moved to the right by the presto permit a return of the valve to its neutral position.

For instance, where the com- In order to furnish a high pressure air supply for operating any auxiliaries, a starting device being one, a tap 94 is made for such purpose into the direct bounce cylinder or cylinders of the engine approximately at the outer or scavenging end thereof. In the present instance, the direct bounce equalizer line H! is provided with an extension 95 leading to an air pressure storage flask 96, which in turn may have connection with any desired air operated auxiliary. A non-return pressure regulator 91 is provided in the extension 95 and this can be set for the desired storage pressure with an upper limit equal to or slightly less than the direct bounce maximum.

I wish it understood that my invention is not limited to any specific construction, arrangement or form of the parts, as it is capable of numerous modifications and changes without departing from the spirit of the claims.

Having thus described my invention, what I claim as new, and desire to secure by United States Letters Patent, is:

l. The combination with an internal combustion free piston engine wherein during an operation thereof several separate air pressures, including direct bounce and scavenging pressures, are present, of a governor for maintaining a properly balanced condition of said bounce and scavenging pressures and including means responsive to a predetermined unbalanced relationship of said pressures to correct such condition by admitting scavenging pressure to the direct bounce pressure to increase the latter when that pressure becomes less than is required to maintain operating conditions and by venting the direct bounce pressure when that pressure becomes greater than is required to maintain operating conditions.

2. The combination with an internal combustion free piston engine wherein during an operasure becomes less than is required to maintain operating conditions and by venting the direct bounce pressure when that pressure becomes greater than is required to maintain operating conditions.

3. The combination with an internal combustion free piston engine wherein during an operation thereof several separate air pressures, including direct bounce and scavenging pressures are present, of a governor for maintaining a substantially predetermined balanced condition of said pressures for proper running upon a change of engine frequency, which governor includes a connection between said bounce and scavenging pressures, valve means normally closing said connection, a normally closed vent for the direct bounce pressure, and means responsive to an unbalanced condition of said pressures to open said valve when the direct bounce pressure is less than required for a proper balanced condition and to open said vent when thedirect bounce pressure is greater than is required for a proper balanced condition.

. 4. The combination with an internal combustion free piston engine wherein a direct bounce present, of a governor for maintaining a substantially predetermined balanced condition of said pressures for proper running upon a change of engine frequency, which governor includes a communicating connection between said bounce and scavenging pressures, a valve closing said connection, a normall closed relief valve for the bounce pressure, and means responsive to an unbalanced condition of said pressures to open the relief valve to reduce the bounce pressure if less air is required and to open said connection valve to increase the bounce pressure when the scavenging pressure predominates and additional air is required to maintain operating equilibrium.

5. The combination with an internal combustion free piston engine wherein during an operation thereof reverse'bounce and scavenging air pressures are present and it is necessary to maintain a substantiall predetermined balanced condition of said pressures for proper engine running, of a governor operable to maintain such condition upon a change of engine conditions and including means responsive to an unbalanced relation of said pressures to correct said condition by admitting scavenging air pressure to the reverse bounce pressure to increase the latter when the former predominates and additional'air is required and to reduce the reverse bounce pressure when less air is required to maintain operating equilibrium.

6. The combination with an internal combustion free piston engine wherein during an oper ation thereof reverse bounce and scavenging air pressures are present and it is necessary to maintain a predetermined condition of said pressures for proper engine running, of a governor operable to maintain such condition upon a change of engine running conditions affecting said pressures, said governor including a communicating connection between said pressures, a valve normally closing said connection, and means responsive to a predetermined unbalan ed condition of said pressure to open said valve to admit scaven ing pressure to the reverse bo nce p essure to increase the latter when the former predominates and additional air is required to maintain operating equilibrium,

7. The combination with an internal combustion free piston engine wherein during an operation thereof reverse bounce and scavenging air pressures are present and it is necessary to maintain a predetermined condition of said pressures for proper engine running, of a governor operable to maintain such condition upon a change of engine running conditions affecting said pressures, said governor including a normally closed relief valve for the reverse bounce pressure, a communicating connection between said pressures, a valve closing said connection and means responsive to a predetermined unbalanced condition of said pressures to open said relief valve to reduce the reverse bounce pressure when less air is required and to open said connecting valve to admit scavenging pressure into the reverse bounce pressure when the former predominates over the latter and additional air is required to maintain operating equilibrium.

8. The combination with an internal combustion free piston engine wherein during an operation thereof reverse bounce and scavenging air pressures are present and it is necessary to maintain a predetermined condition of said pressures for-proper engine running, of a governor operable to maintain such condition upon an engine frequency change, said governor including a communicating connection between said pressures, a

valve normally closing said connection, a relief valve for the reverse bounce pressure, separate fluid pressure responsive means for opening each of said valves, a control valve for the-admission of operating fluid to each of said valve operating means and normally standing in neutral position to prevent such admission and operable to admit operating fluid to one or the other means, and means having connection with said reverse bounce pressure and operable to move said control valve to permit fluid pressure opening of said connecting valve when the scavenging pressure predominates and additional air is required and to permit a fluid pressure opening of said relief valve to reduce the reverse bounce pressure when less air is required to maintain operating equilibrium.

9. An arrangement as called for in claim 8 together with means yieldingly opposing movement of said control valve from neutral position and manually operable to vary the opposing pressure to effect a change in engine speed condition.

10. The combination with an internal combustion free piston engine wherein during an operation thereof reverse bounce and scavenging air pressures are present and it is necessary to maintain a predetermined condition of said pressures for proper engine running, of a governor operable to substantially maintain such condition upon an engine frequency change, said governor including a communicating connection between said pressures and a relief passage for the reverse bounce pressure, separate valves normally closing said connection and passage, fluid operating means for opening each of said valves, a control valve adapted when in neutral position to close the piston operating supply to each of said valve opening means, means yieldingly acting on the control valve to move it in one direction from neutral to permit fluid pressure actuated opening of said connection valve, and means acting on said control valve in opposition to said yielding means and responsive to reverse bounce pressure to move such valve to permit fluid actuated-opening of the relief valve when less air is required and permit movement of the control valve to permit fluid actuated opening of the connectionvalve'to increase the reverse bounce pressure by thezscavenglng pressure when the latterpredominatesand additional air is required to maintain operating equilibrium.

11. The combination with an internal combustion free piston engine wherein during its operation direct bounce, reverse bounce and scavenging air pressures are present, of two governors, one for maintaining a properly balanced condition of all said pressures and the other including means providing connection between the reverse bounce and scavenging air pressures for maintaining predetermined balanced relation between the reverse bounce and scavenging'pressures.

12. The combination with an internal combustion free piston engine wherein during its operation direct bounce, reverse bounce and scavenging air pressures are present, of a governor including means responsive to a predetermined unbalanced relationship of said direct bounce and scavenging pressures to correct such condition by admitting scavenging pressure to the direct bounce pressure to increase the latter when the scavenging pressure predominates and additional air is required and by reducing the direct bounce pressure when less air is required to maintain operabing equilibrium, and a second governor including means responsive to a predetermined unbalanced relationship of said reverse bounce and scavenging pressures to correct such condition by admitting scavenging pressure to the reverse bounce pressure when the former predominates and additional air is required and by reducing the reverse bounce pressure when less air is required to maintain operating equilibrium.

13. The combination with an internal combustion free piston engine wherein direct bounce, reverse bounce, compressor and scavenging air pressures are present during an operation thereof and wherein such pressures must have a predetermined balanced relationship in order to obtain proper running, of a governor responsive to an unbalanced condition of said pressures to correct such condition by admittin scavenging pressure to said direct bounce pressure when the former predominates and additional air is required and to reduce the direct bounce pressure when less air is required to maintain operating equilibrium, and a second governor connecting said reverse bounce and scavenging pressures and operable to admit scavenging pressure to the reverse bounce pressure when the former predominates and additional air is required and to reduce the reverse bounce pressure when less air is required to maintain operating equilibrium.

14. An arrangement as called for in claim 13 together with means manually operable to change the running condition of the engine and to change the balancing action of said reverse bounce and scavenging pressures to suit said changed running condition.

15. The combination with an internal combustion free piston engine wherein durin its operation direct bounce, reverse bounce and scavenging air pressures are present, of a 'governor including means responsive to an unbal- I anced relationship of said direct bounce and scavenging pressures to correct such condition by admitting scavenging pressure to the direct bounce pressure to increase the latter when the' scavenging pressure predominates and additional air is required and by reducing the direct-bounce pressure when less air is required to/maintain operating equilibrium, and a second governor including means responsive to the reverse bounce pressure and operable to increase it when the scavenging pressure predominates and additional ,air is required to lower it when less air is required to maintain operating equilibrium.

16. An arrangement as called for in claim 15 together with means manually operable to change the running condition of the engine and to change the balancing action of said reverse bounce and scavenging pressures to suit said changed running condition.

7 WILLARD A.- MORAIN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS I Date 

